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Photosynthesis: The Calvin Cycle Life from Air 2007- Remember what it means to be a plant… Need to produce all organic molecules necessary for growth carbohydrates, lipids, proteins, nucleic acids Need to store chemical energy (ATP) produced from light reactions in a more stable form that can be moved around plant saved for a rainy day carbon + water + energy glucose + oxygen dioxide 6CO2 + 6H2O + light C6H12O6 + 6O2 energy Light reactions Convert solar energy to chemical energy ATP ATP energy NADPH reducing power What can we do now? build stuff !! photosynthesis How is that helpful? Want to make C6H12O6 synthesis How? From what? What raw materials are available? CO2 NADPH carbon fixation reduces CO2 NADP C6H12O6 NADP From CO2 C6H12O6 CO2 has very little chemical energy fully oxidized C6H12O6 contains a lot of chemical energy highly reduced Synthesis = endergonic process put in a lot of energy Reduction of CO2 C6H12O6 proceeds in many small uphill steps each catalyzed by a specific enzyme using energy stored in ATP & NADPH From Light reactions to Calvin cycle Calvin cycle chloroplast stroma Need products of light reactions to drive synthesis reactions stroma ATP NADPH ATP thylakoid C C Calvin cycle C C C C C 1C C C C C C 3. Regeneration C C C C C of RuBP RuBP starch, sucrose, cellulose & more ribulose bisphosphate 3 ATP H H H | | | C–C–C C C C C C C C C C C C C C C C C C C CO2 1. Carbon fixation C C C C C C RuBisCo ribulose bisphosphate carboxylase 3 ADP used to make glucose C=C=C 5C C C C C C C C 6C C C C C C C 5C glyceraldehyde-3-P G3P C C C PGA phosphoglycerate 3C 6 NADP C C C C C C 6 ATP 2. Reduction 6 NADPH 3C C C C C C C 3C 6 ADP C C C C C C H | H | H | Remember G3P? glycolysis glucose C-C-C-C-C-C 2 ATP 2 ADP fructose-1,6bP P-C-C-C-C-C-C-P DHAP P-C-C-C G3P glyceraldehyde 3-phosphate C-C-C-P 2 NAD+ 2 4 ADP Photosynthesis pyruvate C-C-C 4 ATP To G3P and Beyond! Glyceraldehyde-3-P To G3P and beyond! end product of Calvin cycle energy rich 3 carbon sugar “C3 photosynthesis” G3P is an important intermediate G3P glucose carbohydrates lipids phospholipids, fats, waxes amino acids proteins nucleic acids DNA, RNA RuBisCo Enzyme which fixes carbon from air ribulose bisphosphate carboxylase the most important enzyme in the world! it makes life out of air! definitely the most abundant enzyme I’m green with envy! It’s not easy being green! Accounting The accounting is complicated 3 turns of Calvin cycle = 1 G3P 3 CO2 1 G3P (3C) 6 turns of Calvin cycle = 1 C6H12O6 (6C) 6 CO2 1 C6H12O6 (6C) 18 ATP + 12 NADPH 1 C6H12O6 any ATP left over from light reactions will be used elsewhere by the cell Photosynthesis summary Light reactions produced ATP produced NADPH consumed H2O produced O2 as byproduct Calvin cycle consumed CO2 produced G3P (sugar) regenerated ADP regenerated NADP ADP NADP Light Reactions light ATP + NADPH + O 2 energy H 2O + H2O sunlight Energy Building Reactions NADPH ATP O2 produces ATP produces NADPH releases O2 as a waste product Calvin Cycle CO2 + ATP + NADPH C6H12O6 + ADP + NADP CO2 ADP NADP Sugar Building Reactions NADPH ATP sugars builds sugars uses ATP & NADPH recycles ADP & NADP back to make more ATP & NADPH Putting it all together light CO2 + H2O + energy C6H12O6 + O2 H2O CO2 sunlight ADP Energy NADP Building Reactions Sugar Building Reactions NADPH ATP O2 sugars Plants make both: energy ATP & NADPH sugars even though this equation is a bit of a lie… it makes a better story Energy cycle sun Photosynthesis light CO2 + H2O + energy C6H12O6 + O2 plants CO2 glucose H2O animals, plants ATP C6H12O6 + O2 energy + CO2 + H2O Cellular Respiration The Great Circle of Life,Mufasa! ATP O2 Summary of photosynthesis 6CO2 + 6H2O + light C6H12O6 + 6O2 energy Where did the CO2 come from? Where did the CO2 go? Where did the H2O come from? Where did the H2O go? Where did the energy come from? What’s the energy used for? What will the C6H12O6 be used for? Where did the O2 come from? Where will the O2 go? What else is involved…not listed in this equation? Supporting a biosphere On global scale, photosynthesis is the most important process for the continuation of life on Earth each year photosynthesis… captures 121 billion tons of CO2 synthesizes 160 billion tons of carbohydrate heterotrophs are dependent on plants as food source for fuel & raw materials The poetic perspective… All the solid material of every plant was built by sunlight out of thin air All the solid material of every animal was built from plant material air sun Then all the plants, cats, dogs, elephants & people … are really particles of air woven together by strands of sunlight! If plants can do it… You can learn it! Ask Questions!! 2007-